Production method of carbon monoxide, carbon dioxide reduction electrode, and carbon dioxide reduction device

Abstract

To provide a production method of carbon monoxide having high carbon monoxide selectivity, a carbon dioxide reduction electrode, and a carbon dioxide reduction device.SOLUTION: A production method of carbon monoxide includes a step of reacting carbon dioxide with water in presence of a carbon dioxide reduction catalyst represented by the formula (1) [where R1 is H or a substituent; P1 is a divalent group containing an aromatic ring; Q1 and Q2 are a monovalent group containing an aromatic ring; M is Co, Ni, or Zn; X is a counter ion or a neutral molecule; and O is an oxygen atom and binds with at least one M].SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing carbon monoxide, a carbon dioxide reduction electrode, and a carbon dioxide reduction device. [Background technology]

[0002] In a method for producing carbon monoxide by reducing carbon dioxide, a noble metal such as gold or silver may be used as a carbon dioxide reduction catalyst. For example, Patent Documents 1 and 2 disclose examples in which gold nanoparticles are used as catalysts. On the other hand, complex catalysts in which nitrogen-containing compounds are coordinated to base metals have been attracting attention in recent years. Non-Patent Document 1 describes a method for converting carbon dioxide into carbon monoxide using cobalt phthalocyanine as a catalyst. Non-Patent Document 2 describes a method for converting carbon dioxide into carbon monoxide using a complex having two nickel cyclams in the same molecule as a catalyst. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Nature, 2019, 575, 640 [Non-patent document 2] Green Chem., 2018, 20, 798-803 [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-147677 [Patent Document 2] Special Publication No. 2022-510842 Summary of the Invention [Problem to be solved by the invention]

[0005] The noble metal catalysts described in Patent Documents 1 and 2 are expensive, and there are concerns about increased costs. On the other hand, in the carbon monoxide production methods using complexes containing base metals as carbon dioxide reduction catalysts as described in Non-Patent Documents 1 and 2, a large amount of by-products is likely to be generated, and carbon monoxide selectivity tends to be low.

[0006] An object of one embodiment of the present disclosure is to provide a method for producing carbon monoxide with high carbon monoxide selectivity using a base metal complex as a catalyst. Another problem to be solved by another embodiment of the present disclosure is to provide a carbon dioxide reduction electrode that has high carbon monoxide selectivity. Another problem to be solved by another embodiment of the present disclosure is to provide a carbon dioxide reduction device with high carbon monoxide selectivity. [Means for solving the problem]

[0007] The means for solving the above problems include the following means. <1> A method for producing carbon monoxide, comprising a step of reacting carbon dioxide with water in the presence of a carbon dioxide reduction catalyst represented by the following formula (1):

[0008] [ka] (In formula (1), R 1 represents a hydrogen atom or a substituent, and multiple R 1 may be the same or different, and two adjacent R 1 may be bonded to each other to form a ring, P 1 represents a divalent group containing one or more aromatic rings, and Q 1 and Q 2 represents a monovalent group containing one or more aromatic rings, and Q 1 and Q 2may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

[0009] <2> The above P 1 is expressed by the following formula (P a ), the following formula (P b ) or the following formula (P c ) is a divalent group represented by <1> The method for producing carbon monoxide according to claim 1.

[0010] [ka] (Formula(P a ) ~ expression (P c In the above, R represents a hydrogen atom or a substituent, two adjacent Rs may be bonded to each other to form a ring structure, multiple Rs may be the same or different, two adjacent Rs may be bonded to each other to form a ring, Y represents any of the groups shown below, and multiple Ys may be the same or different, Z represents an alkylene group or an arylene group, and * represents a bond.

[0011] [ka] (In the formula, R a represents a hydrogen atom or a substituent.

[0012] <3> The carbon dioxide reduction catalyst is a compound represented by the following formula (2): <1> The method for producing carbon monoxide according to claim 1.

[0013] [ka] (In formula (2), R 6~R 8 represents a hydrogen atom or a substituent, and two adjacent R 6 Two adjacent Rs 7 Each other and two adjacent R 8 may be bonded to each other to form a ring structure, and multiple R 6 ~R 8 may be the same or different, and Q 3 and Q 4 represents a monovalent group containing one or more aromatic rings, and Q 3 and Q 4 may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

[0014] <4> The carbon dioxide reduction catalyst is a compound represented by the following formula (3): <1> The method for producing carbon monoxide according to claim 1.

[0015] [ka] (In formula (3), R 9 ~R 13 represents a hydrogen atom, a substituent, or a divalent group, and two adjacent R 9 Two adjacent Rs 10 Two adjacent Rs 11 Two adjacent Rs 12 R's, both adjacent to each other 12 and R 13 may be bonded to each other to form a ring structure, Existing R 9 ~R 13 may be the same or different, and R 13is a divalent group, the divalent group may form a bond with another compound represented by formula (3) to form a dimer, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or greater, and when there are multiple Xs, they may be the same or different.

[0016] <5> The carbon dioxide reduction catalyst is a compound represented by the following formula (4): <1> The method for producing carbon monoxide according to claim 1.

[0017] [ka] (In formula (4), R 14 ~R 16 represents a hydrogen atom or a substituent, and two adjacent R 14 Two adjacent Rs 15 R's, both adjacent to each other 15 and R 16 may be linked to each other to form a ring, and multiple R 14 ~R 16 may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple M's may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or greater, and when there are multiple X's, they may be the same or different.

[0018] <6> The carbon dioxide reduction catalyst is a compound represented by the following formula (5): <1> The method for producing carbon monoxide according to claim 1.

[0019] [ka] (In formula (5), R 17 ~R 21 represents a hydrogen atom or a substituent, and two adjacent R 17 Two adjacent Rs 18 Two adjacent Rs 19Two adjacent Rs 21 R's, both adjacent to each other 20 and R 21 may be bonded to each other to form a ring structure, and multiple R 17 ~R 21 may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.

[0020] <7> A carbon dioxide reduction electrode comprising a carbon dioxide reduction catalyst represented by the following formula (1) or a conductive material supporting the carbon dioxide reduction catalyst represented by the following formula (1):

[0021] [ka] (In formula (1), R 1 represents a hydrogen atom or a substituent, and multiple R 1 may be the same or different, and two adjacent R 1 may be bonded to each other to form a ring, P 1 represents a divalent group containing one or more aromatic rings, and Q 1 and Q 2 represents a monovalent group containing one or more aromatic rings, and Q 1 and Q 2 may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

[0022] <8> The carbon dioxide reduction catalyst represented by the formula (1) is supported on a conductive material, and the conductive material is further supported by a support. <7> The carbon dioxide reduction electrode according to claim 1. <9> Further containing an ionic conductor <7> or <8> The carbon dioxide reduction electrode according to claim 1. <10> an oxidation electrode; <7> ~ <9> a membrane separating the oxidation electrode and the carbon dioxide reduction electrode; an electrolyte; and a power source connected to the oxidation electrode and the carbon dioxide reduction electrode. [Effects of the Invention]

[0023] According to one embodiment of the present disclosure, a method for producing carbon monoxide with high carbon monoxide selectivity is provided. According to another embodiment of the present disclosure, a carbon dioxide reduction electrode with high carbon monoxide selectivity is provided. According to another embodiment of the present disclosure, a carbon dioxide reduction device with high carbon monoxide selectivity is provided. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a carbon dioxide reduction electrode according to the present disclosure. [Figure 2] 1 is a schematic cross-sectional view showing an example of a carbon dioxide reduction device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In the numerical ranges described in stages in this specification, The upper or lower limit may be replaced with the upper or lower limit of another stepwise described range. In addition, in the ranges described in this specification, the upper or lower limit of the range may be replaced with the values ​​shown in the examples.

[0026] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified. The term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved.

[0027] Examples of the "substituent" include a halogen atom, an alkyl group (including a cycloalkyl group), an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl group, an aryloxy group, a divalent oxo group, an arylthio group, a monovalent heterocyclic group, a substituted amino group, an acyl group, an imine residue, an amide group, an acid imide group, a substituted oxycarbonyl group, a cyano group, an alkylsulfonyl group, and a nitro group. In this specification, when referring to the number of carbon atoms, the number of carbon atoms does not usually include the number of carbon atoms of the substituent A.

[0028] The term "aromatic hydrocarbon ring group" refers to an atomic group remaining after removing one or more hydrogen atoms directly bonded to carbon atoms constituting an aromatic hydrocarbon ring, which may be unsubstituted or substituted, and which may be condensed with two or more rings.

[0029] The term "aromatic heterocyclic group" refers to an atomic group remaining after removing one or more hydrogen atoms directly bonded to carbon atoms or heteroatoms constituting an aromatic heterocyclic ring, which may be unsubstituted or substituted and may be condensed with two or more rings.

[0030] In the compound names, "t-" means tertiary, "n-" means normal, and "p-" means para position. The dotted portions in the chemical structural formulas represent portions which may be either single bonds or double bonds.

[0031] <Method of producing carbon monoxide> The method for producing carbon monoxide according to the present disclosure includes a step of reacting carbon dioxide with water in the presence of a carbon dioxide reduction catalyst represented by the following formula (1).

[0032] [ka] (In formula (1), R 1 represents a hydrogen atom or a substituent, and multiple R 1 may be the same or different, and two adjacent R 1 may be bonded to each other to form a ring, P 1 represents a divalent group containing one or more aromatic rings, and Q 1 and Q 2 represents a monovalent group containing one or more aromatic rings, and Q 1 and Q 2 may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

[0033] The carbon monoxide production method according to one embodiment of the present disclosure has the above-described configuration, and is therefore a carbon monoxide production method with high carbon monoxide selectivity. The reason for this is presumed to be as follows.

[0034] It is presumed that the production of carbon monoxide using polynuclear metals proceeds by using a polynuclear metal complex having a polynuclear structure in which central metals are adjacent to each other, whereby carbon dioxide coordinates with cobalt atoms, nickel atoms, and / or zinc atoms of the polynuclear metal complex, and the coordinated carbon dioxide reacts with water to produce carbon monoxide. Here, the carbon monoxide production method according to one embodiment of the present disclosure uses a carbon dioxide reduction catalyst represented by formula (1) above. Although the detailed mechanism is unknown, it is presumed that the polynuclear structure in which central metals are adjacent to each other and the coordination environment of the central metal by the macrocyclic ligand suppress the generation of hydrogen and promote the production of carbon monoxide by the reduction of carbon dioxide, resulting in a carbon monoxide production method with high carbon monoxide selectivity.

[0035] (Carbon dioxide reduction catalyst represented by formula (1)) The carbon dioxide reduction catalyst represented by the formula (1) used in the carbon monoxide production method according to the present disclosure will be described below.

[0036] In the formula (1), R 1 is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 1 When R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms (also referred to as "carbon atom number"), and even more preferably a t-butyl group. 1 When is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. In the formula (1), from the viewpoint of carbon monoxide selectivity, the para-position relative to the bonding position of the oxygen atom is R 1 is preferably an alkyl group or an alkoxy group. In addition, in the formula (1), from the viewpoint of carbon monoxide selectivity, R 1 are preferably all hydrogen atoms. In the formula (1), Q 1 and Q 2 Examples of the aromatic ring contained in the monovalent group represented by Q include an aromatic hydrocarbon ring group and an aromatic heterocyclic group. 1 and Q 2 The aromatic heterocyclic group contained in the monovalent group represented by the formula (I) is preferably an aromatic heterocyclic group containing a nitrogen atom or an aromatic heterocyclic group containing a sulfur atom. 1 and Q 2 When they are bonded to each other to form a ring structure, the ring structure is preferably an atomic group remaining after removing two hydrogen atoms from phenanthroline, for example. M represents a cobalt atom, a nickel atom, or a zinc atom, and is preferably a nickel atom from the viewpoint of carbon monoxide selectivity. Furthermore, from the viewpoint of carbon monoxide selectivity, M is preferably a divalent cobalt atom or a divalent nickel atom. The carbon dioxide reduction catalyst represented by the formula (1) may be a heterometal complex. From the viewpoint of reduction efficiency, M is also preferably a combination of a nickel atom and a zinc atom, or a combination of a cobalt atom and a zinc atom. Among these, the metal atom contained in the carbon dioxide reduction catalyst represented by the formula (1) is preferably a nickel atom from the viewpoint of carbon monoxide selectivity. Preferably, a is 2. The counter ion represented by X is preferably an anion, and more preferably at least one anion selected from the group consisting of a fluoride ion, a chloride ion, a bromide ion, an iodide ion, a sulfide ion, an oxide ion, a hydroxide ion, a hydride ion, a sulfite ion, a phosphate ion, a cyanide ion, an acetate ion, a 2-ethylhexanoate ion, a carbonate ion, a sulfate ion, a nitrate ion, a hydrogen carbonate ion, a trifluoroacetate ion, a thiocyanide ion, a trifluoromethanesulfonate ion, an acetylacetonate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, and a tetraphenylborate ion. The neutral molecule represented by X is preferably at least one neutral molecule selected from the group consisting of water, methanol, ethanol, n-propanol, isopropyl alcohol, 2-methoxyethanol, 1,1-dimethylethanol, ethylene glycol, N,N'-dimethylformamide, N,N'-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, acetone, chloroform, acetonitrile, benzonitrile, triethylamine, pyridine, pyrazine, diazabicyclo[2.2.2]octane, 4,4'-bipyridine, tetrahydrofuran, diethyl ether, dimethoxyethane, methyl ethyl ether, 1,4-dioxane, acetic acid, propionic acid, and 2-ethylhexanoic acid. b is preferably an integer of 0 or more and 8 or less, and more preferably an integer of 0 or more and 4 or less.

[0037] In the formula (1), P 1 Examples of the aromatic ring contained in include an aromatic hydrocarbon ring group and an aromatic heterocyclic group. From the viewpoint of carbon monoxide selectivity, the aromatic heterocyclic group is preferably an aromatic heterocyclic group containing a nitrogen atom or an aromatic heterocyclic group containing a sulfur atom, more preferably an aromatic heterocyclic group containing a nitrogen atom, and particularly preferably a five- or six-membered aromatic heterocyclic group containing a nitrogen atom. Also, P 1 From the viewpoint of carbon monoxide selectivity, is preferably a divalent group containing two or more aromatic rings, and more preferably a divalent group containing two aromatic rings. Furthermore, P 1 From the viewpoint of carbon monoxide selectivity, a ), the following formula (P b ), or the following formula (P c ) is preferably a divalent group represented by the formula:

[0038] [ka] (Formula(P a ) ~ expression (P c In the above, R represents a hydrogen atom or a substituent, two adjacent Rs may be bonded to each other to form a ring structure, the multiple Rs may be the same or different, two adjacent Rs may be bonded to each other to form a ring, Y represents any of the groups shown below, and the multiple Ys may be the same or different, Z represents an alkylene group or an arylene group, and * represents a bond.

[0039] [ka] (In the formula, R a represents a hydrogen atom or a substituent.

[0040] The formula (P aIn the above, R at the ortho-position relative to the bonding position between the pyridine rings of the bipyridyl structure is preferably a hydrocarbon group, more preferably an alkyl or alkenyl group having from 1 to 6 carbon atoms, and even more preferably an alkenyl group having from 1 to 4 carbon atoms. It is preferable that the two Rs at the ortho-positions are bonded to each other to form a ring structure, and the ring structure formed by bonding the two Rs at the ortho-positions to each other is preferably a benzene ring. The formula (P a In the above, R at the meta and para positions of the bonding positions between the pyridine rings of the bipyridyl structure is preferably a hydrogen atom.

[0041] The formula (P b In the above, the four Rs on the aromatic heterocycle are preferably hydrogen atoms. The formula (P bIn the above, R in the bridging portion linking two aromatic heterocycles is preferably an aromatic hydrocarbon ring group, preferably an unsubstituted or substituted aromatic hydrocarbon group having 30 or less carbon atoms, more preferably an unsubstituted or substituted phenyl group, an unsubstituted or substituted naphthyl group, an unsubstituted or substituted anthryl group, or an unsubstituted or substituted pyrenyl group, and even more preferably an unsubstituted or substituted phenyl group. Specific examples of the substituent include halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, hydroxy groups, carboxyl groups, ester groups, mercapto groups, sulfonic acid groups, nitro groups, phosphonic acid groups, silyl groups having an alkyl group having 1 to 4 carbon atoms, methyl groups, ethyl groups, propyl groups, isopropyl groups, cyclopropyl groups, butyl groups, isobutyl groups, tert-butyl groups, pentyl groups, cyclopentyl groups, hexyl groups, cyclohexyl groups, norbornyl groups, nonyl groups, cyclononyl groups, and decyl groups. and linear, branched, or cyclic monovalent saturated hydrocarbon groups having a total carbon number of about 1 to 50, such as 3,7-dimethyloctyl, adamantyl, dodecyl, cyclododecyl, pentadecyl, octadecyl, or docosyl groups, and linear, branched, or cyclic alkoxy groups having a total carbon number of about 1 to 50, such as alkenyl, alkynyl, methoxy, ethoxy, propoxy, butoxy, pentyloxy, cyclohexyloxy, norbornyloxy, decyloxy, or dodecyloxy groups. The number of substituents may be any number that allows substitution, and is 1 to 5 for a phenyl group, 1 to 7 for a naphthyl group, and 1 to 9 for each of anthryl and pyrenyl groups.

[0042] The formula (P c In the formula (I), Z is preferably an alkylene group having 2 to 6 carbon atoms or an arylene group having 4 to 14 carbon atoms, more preferably an arylene group having 4 to 14 carbon atoms, and even more preferably an arylene group having 6 to 10 carbon atoms, from the viewpoint of carbon monoxide selectivity. When Z is an alkylene group, Z is preferably a 1,3-propylene group. The arylene group in Z may be a divalent hydrocarbon aromatic group or a divalent heteroaromatic group. When Z is an arylene group, Z is preferably a phenylene group, a pyridinediyl group, a tetrafluorophenylene group, a naphthalenediyl group, a thiophenediyl group, a dimethylphenylene group, or a phenanthrenediyl group, more preferably a 1,2-phenylene group, a 3,4-pyridinediyl group, a 3,4,5,6-tetrafluoro-1,2-phenylene group, a 2,3-naphthalenediyl group, a 3,4-thiophenediyl group, a 3,4-dimethyl-1,2-phenylene group, or a 9,10-phenanthrenediyl group, and particularly preferably a 1,2-phenylene group.

[0043] The formula (P c In terms of carbon monoxide selectivity, R in the formula (I) is preferably a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, or an alkylthio group, and more preferably a hydrogen atom or an alkyl group. When R is an alkyl group, R is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and even more preferably a methyl group or a t-butyl group. When R is an aryl group, R is preferably an aryl group having 6 to 14 carbon atoms, and more preferably a phenyl group. When R is an alkoxy group, R is preferably an alkoxy group having 1 to 10 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms, and even more preferably a methoxy group. When R is an alkylthio group, R is preferably an alkylthio group having 1 to 10 carbon atoms, more preferably an alkylthio group having 1 to 4 carbon atoms, and even more preferably a methylthio group.

[0044] The formula (P c In terms of carbon monoxide selectivity, Y in each of the above formulas is preferably the same group, and more preferably the group shown below.

[0045] [ka]

[0046] R in the above formula a is preferably a hydrogen atom from the viewpoint of carbon monoxide selectivity.

[0047] From the viewpoint of carbon monoxide selectivity, the carbon dioxide reduction catalyst is preferably a compound represented by the following formula (2).

[0048] [ka] (In formula (2), R 6 ~R 8 represents a hydrogen atom or a substituent, and two adjacent R 6 Two adjacent Rs 7 Each other and two adjacent R 8 may be bonded to each other to form a ring structure, and multiple R 6 ~R 8 may be the same or different, and Q 3 and Q 4 represents a monovalent group containing one or more aromatic rings, and Q 3 and Q 4 may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

[0049] In the formula (2), R 6 is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 6 When R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably a t-butyl group. 6When is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. In addition, in the formula (2), from the viewpoint of carbon monoxide selectivity, two R 6 is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in the formula (2), from the viewpoint of carbon monoxide selectivity, four R 6 is preferably a hydrogen atom. In the formula (2), R 7 is preferably a hydrocarbon group, more preferably an alkyl or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. 7 Preferably, two adjacent R 7 The ring structure formed by bonding together is preferably a benzene ring. In the formula (2), R 8 is preferably a hydrogen atom. In the formula (2), Q 3 and Q 4 Examples of the aromatic ring contained in the monovalent group represented by Q include an aromatic hydrocarbon ring group and an aromatic heterocyclic group. 3 and Q 4 The aromatic heterocyclic group contained in the monovalent group represented by the formula (I) is preferably an aromatic heterocyclic group containing a nitrogen atom or an aromatic heterocyclic group containing a sulfur atom. 3 and Q 4 When they are bonded to each other to form a ring structure, the ring structure is preferably an atomic group remaining after removing two hydrogen atoms from phenanthroline, for example. In the formula (2), the preferred embodiments of M, a, X, and b are the same as the preferred embodiments of M, a, X, and b in the formula (1).

[0050] From the viewpoint of carbon monoxide selectivity, the carbon dioxide reduction catalyst is preferably a compound represented by the following formula (3).

[0051] [ka] (In formula (3), R 9 ~R 13 represents a hydrogen atom, a substituent, or a divalent group, and two adjacent R 9 Two adjacent Rs 10 Two adjacent Rs 11 Two adjacent Rs 12 R's, both adjacent to each other 12 and R 13 may be bonded to each other to form a ring structure, and multiple R 9 ~R 13 may be the same or different, and R 13 is a divalent group, the divalent group may form a bond with another compound represented by formula (3) to form a dimer, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or greater, and when there are multiple Xs, they may be the same or different.

[0052] In the formula (3), R 9 is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 9 When R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably a t-butyl group. 9 When is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. In addition, in the formula (3), from the viewpoint of carbon monoxide selectivity, two R 9 is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in the formula (3), from the viewpoint of carbon monoxide selectivity, four R 9 is preferably a hydrogen atom. In the formula (3), R 10 is preferably a hydrocarbon group, more preferably an alkyl or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. 10 Preferably, two adjacent R 10 The ring structure formed by bonding together is preferably a benzene ring. In the formula (3), R 11 is preferably a hydrogen atom. In the formula (3), R 12 is preferably a hydrogen atom. In the formula (3), R 13 is preferably an aromatic hydrocarbon ring group, and is preferably an unsubstituted or substituted aromatic hydrocarbon group having 30 or less carbon atoms. More preferably, the group is a phenyl group having a substituent, an unsubstituted or substituted naphthyl group, an unsubstituted or substituted anthryl group, or an unsubstituted or substituted pyrenyl group, and even more preferably an unsubstituted or substituted phenyl group. Specific examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, a hydroxyl group, a carboxyl group, an ester group, a mercapto group, a sulfonic acid group, a nitro group, a phosphonic acid group, a silyl group having an alkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group, a propyl group, an isopropyl group, a cyclopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a norbornyl group, a nonyl group, a cyclononyl group, and a decyl group. and linear, branched, or cyclic monovalent saturated hydrocarbon groups having a total carbon number of about 1 to 50, such as 3,7-dimethyloctyl, adamantyl, dodecyl, cyclododecyl, pentadecyl, octadecyl, or docosyl groups, and linear, branched, or cyclic alkoxy groups having a total carbon number of about 1 to 50, such as alkenyl, alkynyl, methoxy, ethoxy, propoxy, butoxy, pentyloxy, cyclohexyloxy, norbornyloxy, decyloxy, or dodecyloxy groups. The number of substituents may be any number that allows substitution, and is 1 to 5 for a phenyl group, 1 to 7 for a naphthyl group, and 1 to 9 for each of anthryl and pyrenyl groups. In the formula (3), the preferred embodiments of M, X, and b are the same as the preferred embodiments of M, X, and b in the formula (1).

[0053] From the viewpoint of carbon monoxide selectivity, the carbon dioxide reduction catalyst is preferably a compound represented by the following formula (4).

[0054] [ka] (In formula (4), R 14 ~R 16 represents a hydrogen atom or a substituent, and two adjacent R 14Two adjacent Rs 15 R's, both adjacent to each other 15 and R 16 may be linked to each other to form a ring, and multiple R 14 ~R 16 may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple M's may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or greater, and when there are multiple X's, they may be the same or different.

[0055] In the formula (4), R 14 is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 14 When R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably a t-butyl group. 14 When is an alkoxy group More preferably, it is an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. In addition, in the formula (4), from the viewpoint of carbon monoxide selectivity, two R 14 is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in the formula (4), from the viewpoint of carbon monoxide selectivity, four R 14 is preferably a hydrogen atom. In the formula (4), R 15 is preferably a hydrogen atom. In the formula (4), R 16is preferably an aromatic hydrocarbon ring group, preferably an unsubstituted or substituted aromatic hydrocarbon group having 30 or less carbon atoms, more preferably an unsubstituted or substituted phenyl group, an unsubstituted or substituted naphthyl group, an unsubstituted or substituted anthryl group, or an unsubstituted or substituted pyrenyl group, and even more preferably an unsubstituted or substituted phenyl group. Specific examples of the substituent include halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, hydroxy groups, carboxyl groups, ester groups, mercapto groups, sulfonic acid groups, nitro groups, phosphonic acid groups, silyl groups having an alkyl group having 1 to 4 carbon atoms, methyl groups, ethyl groups, propyl groups, isopropyl groups, cyclopropyl groups, butyl groups, isobutyl groups, tert-butyl groups, pentyl groups, cyclopentyl groups, hexyl groups, cyclohexyl groups, norbornyl groups, nonyl groups, cyclononyl groups, and decyl groups. and linear, branched, or cyclic monovalent saturated hydrocarbon groups having a total carbon number of about 1 to 50, such as 3,7-dimethyloctyl, adamantyl, dodecyl, cyclododecyl, pentadecyl, octadecyl, or docosyl groups, and linear, branched, or cyclic alkoxy groups having a total carbon number of about 1 to 50, such as alkenyl, alkynyl, methoxy, ethoxy, propoxy, butoxy, pentyloxy, cyclohexyloxy, norbornyloxy, decyloxy, or dodecyloxy groups. The number of substituents may be any number that allows substitution, and is 1 to 5 for a phenyl group, 1 to 7 for a naphthyl group, and 1 to 9 for each of anthryl and pyrenyl groups. In the formula (4), the preferred embodiments of M, X, and b are the same as the preferred embodiments of M, X, and b in the formula (1).

[0056] From the viewpoint of carbon monoxide selectivity, the carbon dioxide reduction catalyst is preferably a compound represented by the following formula (5).

[0057] [ka] (In formula (5), R 17 ~R21 represents a hydrogen atom or a substituent, and two adjacent R 17 Two adjacent Rs 18 Two adjacent Rs 19 Two adjacent Rs 21 R's, both adjacent to each other 20 and R 21 may be bonded to each other to form a ring structure, and multiple R 17 ~R 21 may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple M's may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or greater, and when there are multiple X's, they may be the same or different.

[0058] In the formula (5), R 17 is preferably a hydrogen atom, an alkyl group, or an alkoxy group. 17 When R is an alkyl group, it is more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably a t-butyl group. 17 When is an alkoxy group, it is more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably a methoxy group. In addition, in the formula (5), from the viewpoint of carbon monoxide selectivity, two R 17 is preferably a substituent, more preferably an alkyl group or an alkoxy group, and even more preferably an alkyl group. Furthermore, in the formula (5), from the viewpoint of carbon monoxide selectivity, four R 17 is preferably a hydrogen atom. In the formula (5), R 18 is preferably a hydrocarbon group, more preferably an alkyl or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. 18 Preferably, two adjacent R 18The ring structure formed by bonding together is preferably a benzene ring. In the formula (5), R 19 and R 20 is preferably a hydrogen atom. In the formula (5), R 21 is preferably a hydrocarbon group, more preferably an alkyl or alkenyl group having 1 to 6 carbon atoms, and even more preferably an alkenyl group having 1 to 4 carbon atoms. 21 Preferably, two adjacent R 21 The ring structure formed by bonding together is preferably a benzene ring. In the formula (5), the preferred embodiments of M, X, and b are the same as the preferred embodiments of M, X, and b in the formula (1).

[0059] Specific structural formulas of the carbon dioxide reduction catalyst represented by the formula (1) are shown below, but the catalyst is not limited thereto. In the structural formulas below, "t-Bu" means a t-butyl group, "i-Pr" means an isopropyl group, "Et" means an ethyl group, "Me" means a methyl group, "TMS" means a trimethylsilyl group, and " - "OAc" means acetate ion, M represents Ni or Co, and the valence of Ni is divalent (Ni 2+ ), and the valence of Co is divalent (Co 2+ )

[0060] [ka]

[0061] [ka]

[0062] [ka]

[0063]

change

[0064]

change

[0065]

change

[0066]

change

[0067]

change

[0068]

change

[0069]

change

[0070]

change

[0071]

change

[0072]

change

[0073]

change

[0074] (Step of reacting carbon dioxide with water) The method for producing carbon monoxide according to the present disclosure includes a step of reacting carbon dioxide with water in the presence of a carbon dioxide reduction catalyst represented by the formula (1) above. This step is not particularly limited as long as it is a step that can react carbon dioxide with water in the presence of the carbon dioxide reduction catalyst represented by formula (1). However, from the viewpoint of carbon monoxide selectivity, it is preferable to perform this step using a carbon dioxide reduction device that includes an oxidation electrode, a carbon dioxide reduction electrode according to the present disclosure, a membrane separating the oxidation electrode and the carbon dioxide reduction electrode, an electrolyte, and a power source connected to the oxidation electrode and the carbon dioxide reduction electrode. The carbon dioxide reduction device will be described in detail later.

[0075] As a method for reacting carbon dioxide with water using a carbon dioxide reduction device, an oxidation electrode and One example is a method in which a current is passed through the carbon dioxide reduction electrode and carbon dioxide is passed through the device so that it comes into contact with the carbon dioxide reduction electrode, and water contained in the electrolyte of the carbon dioxide reduction device reacts with carbon dioxide on the carbon dioxide reduction electrode.

[0076] <Carbon dioxide reduction electrode> The carbon dioxide reduction electrode according to the present disclosure comprises a carbon dioxide reduction catalyst represented by the formula (1) or a conductive material on which the carbon dioxide reduction catalyst represented by the formula (1) is supported.

[0077] (Carbon dioxide reduction catalyst represented by formula (1)) The cobalt atom, nickel atom, or zinc atom contained in the carbon dioxide reduction catalyst represented by the formula (1) may be an uncharged or charged ion, but from the viewpoint of catalytic activity, it is preferably a divalent cobalt atom or a divalent nickel atom. The carbon dioxide reduction catalyst represented by the formula (1) may be a heterometal complex. From the viewpoint of reduction efficiency, it is also preferable that M is a combination of nickel atom and zinc atom, or a combination of cobalt atom and zinc atom. Among these, the metal atom contained in the carbon dioxide reduction catalyst represented by the formula (1) is preferably a nickel atom from the viewpoint of carbon monoxide selectivity.

[0078] (Conductive materials) The conductive material can be any known material that can support the carbon dioxide reduction catalyst represented by formula (1) without any particular limitations. The carbon dioxide reduction catalyst represented by formula (1) can be supported on a flat or rod-shaped carbonaceous material, metal material, or the like. Alternatively, the carbon dioxide reduction catalyst represented by formula (1) can be supported on a porous carbonaceous material, metal material, or the like, such as carbon paper or a metal mesh. The carbon dioxide reduction catalyst represented by formula (1) can also be supported on a powder material, such as carbon black (CB) or metal particles. That is, the carbon dioxide reduction catalyst represented by formula (1) can be used as a composite material supported on a conductive material. Furthermore, a composite material in which the carbon dioxide reduction catalyst represented by formula (1) is supported on a powder material can be molded by compression or the like. Alternatively, a powder material in which the carbon dioxide reduction catalyst represented by formula (1) is supported on a powder material can be immobilized on a support, such as a flat, rod-shaped, lattice-shaped, or porous carbonaceous material, metal material, or the like.

[0079] The conductive material is not particularly limited, but is preferably a porous carbon material. Examples of conductive materials include carbon particles such as Norit, Ketjen Black, Vulcan, Black Pearl, and acetylene black; fullerenes such as C60 and C70; carbon nanotubes; carbon nanohorns; carbon fibers; graphene; graphene oxide; reduced graphene oxide; and graphene meso sponge.

[0080] The method of loading is not particularly limited, and any known method can be applied, including a method of vacuum-depositing the carbon dioxide reduction catalyst represented by the formula (1) onto a conductive support (conductive material), a method of immersing a conductive support in a dispersion liquid in which the carbon dioxide reduction catalyst represented by the formula (1) is dispersed in a solvent and then drying it, a method of coating a dispersion liquid in which the carbon dioxide reduction catalyst represented by the formula (1) is dispersed in a solvent onto a conductive support, and a method of adding a powdered conductive support to a dispersion liquid in which the carbon dioxide reduction catalyst represented by the formula (1) is dispersed in a solvent and allowing the carbon dioxide reduction catalyst represented by the formula (1) to be adsorbed onto the surface of the powder.

[0081] The amount of the carbon dioxide reduction catalyst represented by the formula (1) supported on the conductive material is preferably an amount such that the mass of cobalt atoms, nickel atoms, or zinc atoms relative to the mass of the conductive material is 1% by mass or more and 50% by mass or less, and more preferably an amount such that the mass of cobalt atoms, nickel atoms, or zinc atoms is 2% by mass or more and 10% by mass or less.

[0082] The amount of the carbon dioxide reduction catalyst represented by the formula (1) supported on the conductive material is preferably an amount such that the mass of the carbon dioxide reduction catalyst represented by the formula (1) relative to the mass of the conductive material is 1 mass % or more and 100 mass % or less, and the carbon dioxide reduction catalyst represented by the formula (1) It is more preferable that the mass of the reduction catalyst is 5% by mass or more and 50% by mass or less.

[0083] The mass of metal atoms (cobalt atoms, nickel atoms, or zinc atoms) relative to the mass of the conductive material is measured using a thermogravimetric differential thermal analyzer (TG-DTA) according to the following procedure. This can be done by measuring the TG-DTA curve using a thermogravimetric differential thermal analyzer in air, raising the temperature from 25° C. or lower to 900° C. at a rate of 10° C. / min.

[0084] (Support) The carbon dioxide reduction electrode according to the present disclosure preferably includes a conductive material on which the carbon dioxide reduction catalyst represented by formula (1) is supported, and further includes a support for supporting the conductive material. The support is preferably conductive, and examples thereof include carbon nanotubes, graphene, carbon black, carbon cloth, carbon paper, glassy carbon, graphite, and tantalum (Ta).

[0085] (ionic conductor) The carbon dioxide reduction electrode according to the present disclosure preferably includes an ion conductor. Known ion conductors can be used without particular limitation. An electrolyte solution in which an ionic substance is dissolved in a solvent such as water may be used, or an ion exchange resin may be used. The ion conductor used between the reduction electrode and the membrane and the ion conductor used between the oxidation electrode and the membrane may be the same or different. Both the electrolyte solution and the ion exchange resin may be used as the ion conductor. Examples of ion conductors include ionomers. Ionomers are polymers neutralized with ions. Preferred ionomers are polymers neutralized with cations such as metals (cationic ionomers) or polymers neutralized with anions (anionic ionomers). Examples of anionic ionomers include Sustainion (manufactured by Dioxide Materials), AEMION (manufactured by Ionomer Innovations), Fumasep (manufactured by FumaTech), and Orion (manufactured by Orion).

[0086] The ion conductor preferably accounts for 10% by mass or more and 200% by mass or less of the mass of the conductive material on which the carbon dioxide reduction catalyst represented by the formula (1) is supported.

[0087] (Other ingredients) The carbon dioxide reduction electrode according to the present disclosure may contain other components in addition to the conductive material, the support, and the ion conductor. Examples of other components include a water-repellent material. Examples of water-repellent materials include fluorine-containing resins, silicon-containing resins, silane coupling agents, and waxes. From the viewpoint of water-repellent effect, fluorine-containing resins are preferred, and examples of fluorine-containing resins include polytetrafluoroethylene.

[0088] (Method of manufacturing a carbon dioxide reduction electrode) The carbon dioxide reduction electrode according to the present disclosure is preferably produced by preparing an electrode ink in which the carbon dioxide reduction catalyst represented by formula (1) or a conductive material supported on the carbon dioxide reduction catalyst represented by formula (1), an ionic conductor as needed, and other components are dispersed in a solvent, and then applying the electrode ink to a support and drying it.

[0089] (An example of a carbon dioxide reduction electrode) FIG. 1 shows an example of a carbon dioxide reduction electrode according to the present disclosure. FIG. 1 is a schematic cross-sectional view of a carbon dioxide reduction electrode according to the present disclosure. In FIG. 1, a carbon dioxide reduction electrode 10 has, on a support 2, a layer 1 containing a conductive material on which a carbon dioxide reduction catalyst represented by the above formula (1) is supported. When components other than the ion conductor are contained, these components are contained in layer 1 containing a conductive material supporting the carbon dioxide reduction catalyst represented by the above formula (1).

[0090] <Carbon dioxide reduction device> The carbon dioxide reduction device according to the present disclosure comprises: an oxidation electrode; a carbon dioxide reduction electrode according to the present disclosure; a membrane separating the oxidation electrode and the carbon dioxide reduction electrode; An electrolyte; a power source connected to the oxidation electrode and the carbon dioxide reduction electrode.

[0091] (An example of a carbon dioxide reduction device) FIG. 2 shows an example of a carbon dioxide reduction device according to the present disclosure. 2, the carbon dioxide reduction device 100 includes an oxidation electrode 11, a carbon dioxide reduction electrode 10, a membrane 12 separating the oxidation electrode 11 and the carbon dioxide reduction electrode 10, an electrolyte 13, and a power supply 14 connected to the oxidation electrode 11 and the carbon dioxide reduction electrode 10. The carbon dioxide reduction device 100 also includes an electrolytic cell 15 equipped with these components, and a reaction cell 16. Here, the carbon dioxide reduction electrode 10 is preferably placed so that the conductive material carrying the carbon dioxide reduction catalyst represented by the formula (1) is in contact with the electrolytic solution 13 .

[0092] The carbon dioxide reduction device 100 is applicable to a reaction in which carbon dioxide is reduced to produce carbon monoxide. When used in this reaction, it is preferable to use a power source 14 to pass a current from the carbon dioxide reduction electrode 10 to the oxidation electrode 11. It is then preferable to pass carbon dioxide into the reaction vessel 16 in the direction of arrow A. The carbon dioxide that has flowed into the reaction vessel 16 comes into contact with the carbon dioxide reduction catalyst represented by the above formula (1) in the carbon dioxide reduction electrode 10. This causes the reaction represented by the following reaction formula 1 to proceed on the carbon dioxide reduction electrode 10 side, and the reaction represented by the following reaction formula 2 to proceed on the oxidation electrode 11 side. Reaction 1: CO2 + H2O + 2e - →CO+2OH - Reaction 2: 2OH - →1 / 2O2+H2O+2e - The produced carbon monoxide then flows out of the reaction vessel 16 in the direction of arrow B.

[0093] The carbon dioxide reduction electrode will be described in detail below, with the reference numerals omitted.

[0094] (oxidation electrode) The oxidation electrode may be any known electrode, and is not particularly limited thereto. However, an electrode that generates oxygen by oxidizing water or hydroxide ions is preferred. Examples include, but are not limited to, porous materials made of metal materials such as titanium and nickel, and carbonaceous materials such as carbon paper. The oxidation electrode may contain a metal such as platinum, palladium, or nickel, or a metal oxide such as nickel oxide, iridium oxide, or ruthenium oxide to promote oxygen generation.

[0095] (carbon dioxide reduction electrode) The carbon dioxide reduction electrode used is the carbon dioxide reduction electrode according to the present disclosure described above.

[0096] (film) The membrane separating the carbon dioxide reduction electrode and the oxidation electrode may be any known material, and is not particularly limited, but may be made of an ion-conductive material, such as a porous polymer membrane such as PTFE, a porous membrane such as a glass filter, a cation exchange membrane such as Nafion, or the like. Anion exchange membranes such as Sustainion, Neosepta, and Selemion can be used. Although not particularly limited to these, ion exchange membranes are preferred. As the ion exchange membrane, an anion exchange membrane is more preferred.

[0097] (electrolyte) The electrolyte may be any known electrolyte, and is not particularly limited. Examples include an electrolyte containing cations such as sodium ions and potassium ions, anions such as bicarbonate ions, carbonate ions, hydroxide ions, sulfate ions, phosphate ions, and borate ions, and water.

[0098] The ion concentration of the electrolyte is preferably 0.01 mol / L or more and 5.0 mol / L or less, and more preferably 0.5 mol / L or more and 2.0 mol / L or less.

[0099] (power supply) A power supply is connected to the oxidation electrode and the carbon dioxide reduction electrode. The power source is not particularly limited as long as it can pass a current between the carbon dioxide reduction electrode and the oxidation electrode. As the power source, for example, an electrochemical analyzer 701C manufactured by BAS Corporation can be used. [Example]

[0100] The present disclosure will be described in more detail below using examples, etc., but these are illustrative and the present disclosure is not limited thereto. That is, those skilled in the art can implement the present disclosure by making various modifications to the examples shown below. For example, the materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be modified as appropriate without departing from the spirit of the present disclosure. Note that the values ​​of various manufacturing conditions and evaluation results in the following examples represent preferred upper or lower limit values ​​in the embodiments of the present disclosure, and preferred ranges represent preferred values ​​of the above-mentioned upper or lower limit values. The preferred range may be a range defined by a combination of the above-mentioned upper or lower limit values ​​and the values ​​of the following examples or values ​​between examples. Note that in the following description, unless otherwise specified, all "parts" and "%" are based on mass.

[0101] The performance of the carbon dioxide reduction electrodes prepared by the methods described in the Examples and Comparative Examples was evaluated using a carbon dioxide reduction device 100 shown in FIG. 2. A platinum mesh was used as the oxidation electrode 11. A carbon dioxide reduction electrode was used as the reduction electrode 10. An anion exchange membrane (Sustainion, manufactured by Dioxide Materials) was used as the membrane 12. A 1.0 M (=1.0 mol / L) potassium hydroxide aqueous solution was used as the electrolyte 13. An electrochemical measurement device (Electrochemical Analyzer 701C, manufactured by BAS Corporation) was used as the power source 14. Furthermore, a Hg / HgO reference electrode (manufactured by EC Frontier Co., Ltd.) was placed in the electrolyte 13 between the membrane 12 and the reduction electrode 10 as a reference electrode. Carbon dioxide gas was circulated at a rate of 15 mL / min in the direction of arrow A in the reaction vessel 16, and a constant potential was applied to the reduction electrode 10 using the electrochemical measurement device to perform electrochemical measurements. A 50 μL sample of the outlet gas (gas flowing out of the reaction vessel 16 in the direction of arrow B) was collected using a gas-tight syringe, and the products contained in the gas were quantitatively analyzed using a gas chromatograph (Shimadzu Corporation GC-2010 / BID detector). The Faraday efficiency of each product was calculated as the ratio of the charge used to generate each observed product to the total charge used in the reaction. A higher Faraday efficiency for carbon monoxide indicates more selective carbon monoxide production, implying higher carbon monoxide selectivity.

[0102] <Synthesis Example 1> Polynuclear metal complex 1 was synthesized according to the method described in JP-A-2009-173627 in accordance with the reaction formula shown below.

[0103] [ka]

[0104] <Synthesis Example 2> Polynuclear metal complex 2 was synthesized according to the method described in JP-A-2009-173627 in accordance with the reaction formula shown below.

[0105] [ka]

[0106] <Synthesis Example 3> (Synthesis of Compound 3) Compound 3 was synthesized according to the reaction scheme shown below.

[0107] [ka]

[0108] Under a nitrogen atmosphere, 92 mL of dehydrated toluene and N,N-dimethylanilinium tetrakispentafluorophenylborate (PhNH + Me2B(C6F5)4 - 231 mg (0.29 mmol) of pyrene-1-carbaldehyde was added, and the resulting solution was heated to 80°C while stirring using a rotor. A mixture of 2.09 g (9.06 mmol) of pyrene-1-carbaldehyde, 5.0 g (8.24 mmol) of compound 2, and 12 mL of toluene was added dropwise to this solution. After stirring for 3 hours, the mixture was allowed to cool, and the temperature of the reaction solution was gradually adjusted to room temperature.

[0109] To the reaction mixture, a solution of 0.98 g (9.06 mmol) of benzoquinone dissolved in 11 mL of tetrahydrofuran (THF) was added dropwise. After confirming the completion of the reaction, the resulting reaction mixture was filtered to obtain the target compound 3 in an amount of 5.89 g and a yield of 99%. The identification data for the resulting compound 3 are shown below. The results of ESI-MS measurement were confirmed as follows. ESI-MS [M+H] + :m / z=817.4

[0110] <Synthesis Example 4> (Synthesis of polynuclear metal complex 3) Polynuclear metal complex 3 was synthesized according to the reaction scheme shown below.

[0111] [ka]

[0112] After creating a nitrogen gas atmosphere inside the reaction vessel, 0.34 g (1.35 mmol) of nickel acetate tetrahydrate (Ni(OAc)2·4H2O) was suspended in 10 mL of pre-degassed methanol (MeOH). 10 mL of chloroform (CHCl3) was added to this suspension and the temperature was raised to 50°C to prepare a nickel acetate solution. Another reaction vessel was then created with a nitrogen gas atmosphere, and a suspension consisting of 0.5 g (0.61 mmol) of compound 3 and 30 mL of chloroform was prepared. This suspension was added dropwise to the nickel acetate solution, then heated to 55°C and stirred under reflux for 1 hour to obtain a reaction solution containing polynuclear metal complex 3. This reaction solution was cooled to room temperature and then filtered. The obtained crystals were washed with methanol and dried under reduced pressure to obtain 0.22 g of polynuclear metal complex 3 in a yield of 35%. The identification data for the obtained polynuclear metal complex 3 are shown below. The results of ESI-MS measurement were confirmed as follows. ESI-MS [M-OAc] + :m / z=929.3

[0113] <Synthesis Example 5> (Synthesis of polynuclear metal complex 4) Polynuclear metal complex 4 was synthesized according to the reaction scheme shown below.

[0114] [ka]

[0115] After purging the reaction vessel with nitrogen gas, 0.34 g (1.35 mmol) of cobalt acetate tetrahydrate (Co(OAc)2·4H2O) was suspended in 10 mL of degassed methanol. 10 mL of chloroform was added to this suspension and heated to 50 °C to prepare a cobalt acetate solution. Another reaction vessel was purged with nitrogen gas, and a suspension consisting of 0.5 g (0.61 mmol) of compound 3 and 30 mL of chloroform was prepared. This suspension was added dropwise to the cobalt acetate solution, heated to 55 °C, and stirred under reflux for 1 hour to obtain a reaction solution containing polynuclear metal complex 4. This reaction solution was cooled to room temperature and filtered. The resulting crystals were washed with methanol and dried under reduced pressure to obtain 0.29 g of polynuclear metal complex 4 in a 48% yield. The identification data for the resulting polynuclear metal complex 4 are shown below. The ESI-MS analysis results were confirmed as follows. ESI-MS[M] + :m / z=931.2

[0116] <Synthesis Example 6> Compound 4 was synthesized according to the reaction scheme shown below.

[0117] [ka]

[0118] Under a nitrogen atmosphere, 37 mL of dehydrated toluene and 264 mg (0.33 mmol) of N,N-dimethylanilinium tetrakispentafluorophenylborate were added, and the resulting solution was heated to 80°C with stirring using a rotor. To this solution was added dropwise a mixture of 0.60 g (3.63 mmol) of 2,5-dimethoxybenzaldehyde, 2.0 g (3.30 mmol) of compound 2, and 5 mL of toluene. After stirring for 3 hours, the mixture was allowed to cool, and the temperature of the reaction mixture was gradually adjusted to room temperature.

[0119] To the reaction mixture, a solution of 0.39 g (3.63 mmol) of benzoquinone dissolved in 5 mL of THF was added dropwise. After confirming the completion of the reaction, the resulting reaction mixture was filtered to obtain the target compound 4 in an amount of 2.27 g and a yield of 91%. The identification data for the resulting compound 4 are shown below. The results of ESI-MS measurement were confirmed as follows. ESI-MS [M+H] + :m / z=753.3

[0120] <Synthesis Example 7> (Synthesis of polynuclear metal complex 5) Polynuclear metal complex 5 was synthesized according to the reaction scheme shown below.

[0121] [ka]

[0122] After purging the reaction vessel with nitrogen gas, 0.22 g (0.88 mmol) of nickel acetate tetrahydrate was suspended in 10 mL of degassed methanol. 10 mL of chloroform was added to this suspension and heated to 50 °C to prepare a nickel acetate solution. Another reaction vessel was purged with nitrogen gas, and a suspension consisting of 0.3 g (0.40 mmol) of compound 4 and 30 mL of chloroform was prepared. This suspension was added dropwise to the nickel acetate solution, heated to 55 °C, and stirred under reflux for 1 hour to obtain a reaction solution containing polynuclear metal complex 5. This reaction solution was cooled to room temperature and filtered. The filtrate was concentrated to dryness and washed with acetone to obtain 0.27 g of polynuclear metal complex 5 in a 72% yield. The identification data for the resulting polynuclear metal complex 5 are shown below. The results of ESI-MS analysis were confirmed as follows. ESI-MS [M-OAc] + :m / z=865.3

[0123] <Synthesis Example 8> Using compound 5 synthesized by the method described in JP-A-2009-173627, polynuclear metal complex 6 was synthesized according to the reaction formula shown below.

[0124] [ka]

[0125] After creating a nitrogen gas atmosphere in the reaction vessel, 0.25 g (1.00 mmol) of nickel acetate tetrahydrate was suspended in 10 mL of degassed methanol. 10 mL of chloroform was added to this suspension and heated to 50 °C to prepare a nickel acetate solution. Another reaction vessel was then created under a nitrogen gas atmosphere, and a suspension consisting of 0.3 g (0.40 mmol) of compound 5 and 30 mL of chloroform was prepared. This suspension was added dropwise to the nickel acetate solution, heated to 55 °C, and stirred under reflux for 1 hour to obtain a reaction solution containing polynuclear metal complex 6. This reaction solution was cooled to room temperature and filtered. The filtrate was concentrated to dryness and washed with methanol to obtain 0.28 g of polynuclear metal complex 6 in 84% yield. The identification data for the resulting polynuclear metal complex 6 are shown below. The results of ESI-MS analysis were confirmed as follows. ESI-MS [M+H] + :m / z=847.3

[0126] <Synthesis Example 9> Polynuclear metal complex 7 was synthesized according to the method described in JP-A-2009-173627 in accordance with the reaction formula shown below.

[0127] [ka]

[0128] <Synthesis Example 10> Compound 6 was synthesized according to the reaction scheme shown below using Compound 1 synthesized by the method described in JP-A-2009-173627.

[0129] [ka]

[0130] After purging the reaction vessel with nitrogen gas, 10.00 g (14.43 mmol) of compound 1 was suspended in 370 g of chloroform (CHCl3) and then heated to 50 °C. Another reaction vessel was purged with nitrogen gas, and a suspension consisting of 2.65 g (14.43 mmol) of zinc acetate (Zn(OAc)2) and 90 g of methanol (MeOH) was prepared. The zinc acetate suspension was added dropwise to the suspension of compound 1, and the temperature was raised to 55 °C and stirred under reflux for 1 hour to obtain a reaction solution containing compound 2. After cooling the reaction solution to room temperature, water was added, stirred for a while, and washed, and the aqueous phase was removed. Heptane was added to the resulting organic phase, concentrated, and then filtered. The resulting crystals were dried under reduced pressure to obtain compound 6 (10.9 g, 100% yield). The identification data for the resulting compound 2 are shown below. The results of MALDI-MS analysis were confirmed as follows. MALDI-MS [M+H] + :m / z=756.23

[0131] <Synthesis Example 11> Polynuclear metal complex 8 was synthesized according to the reaction scheme shown below.

[0132] [ka]

[0133] After purging the reaction vessel with nitrogen gas, 2.00 g (2.65 mmol) of compound 6 was suspended in 200 g of chloroform (CHCl3) and then heated to 50 °C. A separate reaction vessel was purged with nitrogen gas, and a suspension consisting of 0.66 g (2.65 mmol) of nickel acetate tetrahydrate (Ni(OAc)2·4H2O) and 40 g of methanol (MeOH) was prepared. The nickel acetate suspension was added dropwise to the suspension of compound 2, then heated to 55 °C and stirred under reflux for 1.5 hours to obtain a reaction solution containing polynuclear metal complex 2. The reaction solution was cooled to room temperature and filtered. The resulting crystals were washed with methanol and dried under reduced pressure to obtain 1.91 g of polynuclear metal complex 2 in an 83% yield. The identification data for the resulting polynuclear metal complex 8 are shown below. The results of MALDI-MS analysis were confirmed as follows. MALDI-MS [M-OAc] + :m / z=813.9

[0134] <Synthesis Example 12> Polynuclear metal complex 9 was synthesized according to the reaction scheme shown below.

[0135] [ka]

[0136] After purging the reaction vessel with nitrogen gas, 2.00 g (2.65 mmol) of compound 6 was suspended in 200 g of chloroform (CHCl3) and then heated to 50 °C. A separate reaction vessel was purged with nitrogen gas, and a suspension consisting of 0.66 g (2.65 mmol) of cobalt acetate tetrahydrate (Co(OAc)2·4H2O) and 40 g of methanol (MeOH) was prepared. The cobalt acetate suspension was added dropwise to the suspension of compound 2, then heated to 55 °C and stirred under reflux for 2 hours to obtain a reaction solution containing polynuclear metal complex 8. After cooling the reaction solution to room temperature, 40 g of methanol containing 0.27 g (2.65 mmol) of triethylamine was added and the mixture was filtered. The resulting crystals were washed with methanol and dried under reduced pressure to obtain 1.55 g of polynuclear metal complex 8 in 67% yield. The identification data for the resulting polynuclear metal complex 8 are shown below. The results of MALDI-MS analysis were confirmed as follows. MALDI-MS [M-OAc] + :m / z=812.1

[0137] <Synthesis Example 13> Compound 7 was synthesized by the method described in Tetrahedron, 1999, 55, 8377. Polynuclear metal complex 10 was synthesized according to the reaction scheme shown below.

[0138] [ka]

[0139] After creating a nitrogen gas atmosphere in the reaction vessel, 1.75 g (7.04 mmol) of nickel acetate tetrahydrate was suspended in 10 mL of methanol (MeOH) and 5 mL of chloroform (CHCl3). To this nickel acetate suspension, 101 mL of a chloroform solution containing 1.50 g (2.82 mmol) of compound 7 was added with stirring, and the mixture was heated to reflux. Next, 10 mL of a chloroform solution containing 0.30 g (2.82 mmol) of 1,2-phenylenediamine was gradually added, and the mixture was refluxed for 3 hours. The solution was concentrated using an evaporator, and then acetone was added. The mixture was cooled to room temperature and filtered. The resulting crystals were washed with acetone and dried under reduced pressure to obtain polynuclear metal complex 9 (1.68 g, 71% yield). The identification data for the resulting polynuclear metal complex 10 are shown below. The results of MALDI-MS analysis were confirmed as follows. MALDI-MS[M] + :m / z=718.14

[0140] Example 1 -Preparation of carbon dioxide reduction electrode (1)- 250 mg of carbon black (KetjenBlack EC600JD, manufactured by Lion Specialty Chemicals Co., Ltd.) was weighed out as a conductive material into a reaction vessel. Polynuclear metal complex 1 was weighed out into a separate reaction vessel so that the mass of nickel atoms was 5% by mass relative to the carbon black, and chloroform was added to confirm that a solution of polynuclear metal complex 1 had been formed. After that, the solution was transferred to the reaction vessel in which the conductive material had been weighed out and formed into a dispersion. Ultrasonic irradiation of this dispersion yielded a suspension in which the conductive material carrying the carbon dioxide reduction catalyst was uniformly dispersed. The suspension was filtered using a filter and then dried under reduced pressure to obtain conductive material 1 carrying the carbon dioxide reduction catalyst.

[0141] A dispersion was prepared by adding 20.0 mg of the conductive material 1 powder, 2.50 mL of ethanol, and 400 mg of a 5% ethanol solution of Sustainion (manufactured by Dioxide Materials) as an anionic ionomer, which is an ion conductor, to a screw tube. Ultrasonic waves were applied to this dispersion to obtain an ink. Carbon paper (25 mm diameter) was used as a support, and 250 mg of the ink obtained above was applied to the carbon paper, which was then dried to obtain a carbon dioxide reduction electrode (1).

[0142] <Example 2, Example 3, Comparative Example 1 and Comparative Example 2> -Preparation of carbon dioxide reduction electrodes (2), (3), (1'), and (2')- Carbon dioxide reduction electrodes (2), (3), (1′), and (2′) were obtained in the same manner as in Example 1, except that the metal complexes, conductive materials, ion conductors, and supports were used in the combinations shown in Table 1 below.

[0143] Example 4 -Preparation of carbon dioxide reduction electrode (4)- A carbon dioxide reduction electrode (4) was obtained in the same manner as in Example 1, except that 100 mg of a 5% solution of Nafion (manufactured by Aldrich Co.) was used as the ion conductor as a cationic ionomer.

[0144] <Examples 5 to 11 and Comparative Example 3> -Preparation of carbon dioxide reduction electrodes (5) to (11) and (3')- Carbon dioxide reduction electrodes (5) to (11) and (3′) were obtained in the same manner as in Example 4, except that the metal complexes, conductive materials, ion conductors, and supports were used in the combinations shown in Table 1 below.

[0145] [Table 1]

[0146] <Evaluation results> Electrochemical measurements were carried out by the method described above using the carbon dioxide reduction electrodes obtained in Examples 1 to 11 and Comparative Examples 1 to 3. Table 2 shows the results.

[0147] [Table 2]

[0148] From the above results, it can be seen that the carbon oxide production method of this example has higher carbon monoxide selectivity than the comparative example. [Explanation of symbols]

[0149] 1: Layer containing a conductive material carrying a carbon dioxide reduction catalyst, 2: Support, 10: Carbon dioxide reduction electrode, 11: Oxidation electrode, 12: Membrane, 13: Electrolyte, 14: Power source, 15: Electrolytic cell, 16: Reactor, 100: Carbon dioxide reduction device

Claims

1. The method includes a step of reacting carbon dioxide with water in the presence of a carbon dioxide reduction catalyst represented by the following formula (1): Carbon monoxide production method. 【Chemical 1】 (In formula (1), R １ represents a hydrogen atom or a substituent, and a plurality of R １ may be the same or different, and two adjacent R １ may be bonded to each other to form a ring, P １ represents a divalent group containing one or more aromatic rings, and Q １ and Q ２ represents a monovalent group containing one or more aromatic rings, and Q １ and Q ２ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

2. The P １ is expressed by the following formula (P ａ ), the following formula (P ｂ ) or the following formula (P ｃ 2. The method for producing carbon monoxide according to claim 1, wherein R is a divalent group represented by the formula (I). 【Chemistry 2】 (Formula (P ａ ) ~ formula (P ｃ In the above, R represents a hydrogen atom or a substituent, two adjacent Rs may be bonded to each other to form a ring structure, the multiple Rs may be the same or different, and two adjacent Rs may be bonded to each other to form a ring, Y represents any of the groups shown below, and the multiple Ys may be the same or different, Z represents an alkylene group or an arylene group, and * represents a bond. 【Chemistry 3】 (In the formula, R ａ represents a hydrogen atom or a substituent.

3. The method for producing carbon monoxide according to claim 1, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (2): 【Chemistry 4】 (In formula (2), R ６ ~R ８ represents a hydrogen atom or a substituent, and two adjacent R ６ Two adjacent Rs ７ Each other and two adjacent R ８ may be bonded to each other to form a ring structure, and multiple R ６ ~R ８ may be the same or different, and Q ３ and Q ４ represents a monovalent group containing one or more aromatic rings, and Q ３ and Q ４ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

4. The method for producing carbon monoxide according to claim 1, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (3): 【Chemistry 5】 (In formula (3), R ９ ~R １３ represents a hydrogen atom, a substituent, or a divalent group, and two adjacent R ９ Two adjacent Rs １０ Two adjacent Rs １１ Two adjacent Rs １２ R １２ and R １３ may be bonded to each other to form a ring structure, and multiple R ９ ~R １３ may be the same or different, R １３ is a divalent group, the divalent group may form a bond with another compound represented by formula (3) to form a dimer, M represents a cobalt atom, a nickel atom, or a zinc atom, and multiple Ms may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different.

5. The method for producing carbon monoxide according to claim 1, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (4): 【Chemistry 6】 (In formula (4), R １４ ~R １６ represents a hydrogen atom or a substituent, and two adjacent R １４ Two adjacent Rs １５ R １５ and R １６ may be linked to each other to form a ring, and multiple R １４ ~R １６ may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, and a plurality of M's may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are a plurality of X's, they may be the same or different.

6. The method for producing carbon monoxide according to claim 1, wherein the carbon dioxide reduction catalyst is a compound represented by the following formula (5): 【Chemistry 7】 (In formula (5), R １７ ~R ２１ represents a hydrogen atom or a substituent, and two adjacent R １７ Two adjacent Rs １８ Two adjacent Rs １９ Two adjacent Rs ２１ R ２０ and R ２１ may be bonded to each other to form a ring structure, and multiple R １７ ~R ２１ may be the same or different, M represents a cobalt atom, a nickel atom, or a zinc atom, and a plurality of M's may be the same or different, X represents a counter ion or a neutral molecule, and b is an integer of 0 or more, and when there are a plurality of X's, they may be the same or different.

7. A carbon dioxide reduction catalyst represented by the following formula (1) or a conductive material supporting the carbon dioxide reduction catalyst represented by the following formula (1), Carbon dioxide reduction electrode. 【Chemistry 8】 (In formula (1), R １ represents a hydrogen atom or a substituent, and a plurality of R １ may be the same or different, and two adjacent R １ may be bonded to each other to form a ring, P １ represents a divalent group containing one or more aromatic rings, and Q １ and Q ２ represents a monovalent group containing one or more aromatic rings, and Q １ and Q ２ may bond to each other to form a ring structure, M represents a cobalt atom, a nickel atom, or a zinc atom, a is an integer of 2 or more and 4 or less, and multiple Ms may be the same or different, X is a counter ion or a neutral molecule, b is an integer of 0 or more, and when there are multiple Xs, they may be the same or different, and O is an oxygen atom and is bonded to at least one M.

8. a conductive material supporting the carbon dioxide reduction catalyst represented by formula (1), The carbon dioxide reduction electrode according to claim 7, further comprising a support for supporting the conductive material.

9. 9. The carbon dioxide reduction electrode according to claim 7 or 8, further comprising an ion conductor.

10. an oxidation electrode; The carbon dioxide reduction electrode according to claim 7 or 8, a membrane separating the oxidation electrode and the carbon dioxide reduction electrode; An electrolyte; a power source connected to the oxidation electrode and the carbon dioxide reduction electrode. Carbon dioxide reduction device.

Images